This invention relates to the production of compounds comprising ether linkages (--C--O--C--). In particular, this invention relates to the production of alkyl-tertiary-alkyl ethers.
Alkyl-tertiary-alkyl ethers are useful as octane improvers for liquid fuels, such as, for example, gasoline. Also, because of the low vapor pressure of alkyl-tertiary-alkyl ethers, they are particularly useful for reducing the vapor pressure of gasoline.
Federal government regulations require that some gasolines contain greater concentration levels of oxygen-containing compounds. Alkyl-tertiary-alkyl ethers have been found to be especially suitable for assisting in the compliance with these Federal regulations.
While processes for the production of alkyl-tertiary-alkyl ethers are known in the art, not all problems associated with such processes have been solved. For example, refinery-catalytic-cracker-hydrocarbon streams, which are typically used for the production of alkyl-tertiary-alkyl ethers, contain undesirable compounds, such as, for example, nitriles. Specific examples of these nitriles are acetonitrile (CH.sub.3 CN also known as methyl cyanide) and propionitrile (C.sub.2 H.sub.5 CN also known as ethyl cyanide). These nitriles are undesirable because they can poison an acidic-ion-exchange-resin catalyst being used in an etherification process. At levels as low as about 15 to about 30 parts per million by weight based on the total weight of a feed stream to an etherification reactor, a typical acidic-ion-exchange-resin-catalyst bed could be deactivated in as little as three months. Replacement of an acidic-ion-exchange-resin-catalyst bed could cost from about 100,000 to about 200,000 U.S. Dollars for a typical fixed-bed reactor to as high as 1,000,000 U.S. Dollars for a complex catalytic-distillation reactor. Consequently, a more efficient etherification process that reduces the amount of acidic-ion-exchange-resin catalyst that is deactivated by such nitriles would be of great value both economically and technologically.